1. The Field of the Invention
The present application is directed to devices for mixing and dispensing medical and dental compositions. More particularly, the application is directed to methods and devices for mixing and dispensing multi-part medical and dental compositions while permitting air or gas to be vented.
2. The Relevant Technology
Many modem formulations are packaged in two parts, often known as A and B components. Upon mixing, the A and B components typically undergo a chemical reaction which causes the resultant composition to “set up” or “cure” in some desired manner. In the dental field, for example, several two-part formulations currently enjoy wide use, such as glass ionomer cements and resinous luting cements. Dental impression materials are also typically made using A and B components.
In order to function properly, it is important that the A and B components of two-component systems be mixed together rapidly and thoroughly and in the right proportions. Failure to rapidly mix the components can result in loss of valuable working time with the resultant composition, and can impact the ability to obtain a thorough mix as the composition may begin to set up unevenly. Failure to mix thoroughly can result in a composition having less than optimum characteristics. For example, if a poorly mixed composition is used as a cement, it is possible that portions of the cement will fail to reach the chemical strength required for a long-term bond.
Problems of obtaining rapid and uniform mixing are often complicated by differences in the A and B components. It is often necessary to mix two liquids, while other times it is necessary to mix a powder with a liquid. Sometimes there are equal amounts of the A and B components, but in other cases there is more of one component than another. Additionally, the two components may have similar viscosities or widely differing viscosities. Components having greatly differing viscosities or other physical properties are typically harder to mix than components having similar physical properties.
One method employed for mixing multiple components has been simple mechanical mixing, through the use of a mixing bowl or pad and a stir instrument such as a spatula. This method tends to be somewhat messy and time consuming. It also is difficult at times to determine whether the mixing has been sufficiently thorough.
An alternative and generally superior system uses two syringes, and optionally a coupler between the two syringes. The distal end of each syringe is coupled to the coupler or directly to the other syringe. The components may be passed back and forth between the syringes in order to mix the components.
It is difficult in many instances to prevent formation of small air or gas bubbles in the mixed composition. With some components, an air or gas bubble may develop within the syringe during storage. In addition, gaseous products may be generated as a result of mixing some A and B components. Such entrapped air or gas bubbles, either within the separate syringes before mixing or within the mixed composition after mixing, can be detrimental.
It would be an advantage to provide a plunger assembly for use with a syringe system that would allow the user to vent air and/or gas bubbles when needed (e.g., before and/or after mixing).